/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/NiagaraSystemViewModel.h
Keeps track of the emitters that are pinned in the stack UI, for persistence
[TArray](API\Runtime\Core\Containers\TArray)< [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [FNiagaraEmitterHandleViewModel](API\Plugins\NiagaraEditor\ViewModels\FNiagaraEmitterHandleViewModel) > > GetPinnedEmitterHandles()